A Redwood City apartment building lacking a key piece of fire-safety equipment burned last week — the second such incident since July — raising questions about the need for fire sprinklers.

Like tens of thousands of Bay Area apartment buildings, the 73-unit Terrace Apartments, built in 1963, was not required to have sprinklers. A nearly identical fire at a ’60s-era building blocks away, also without sprinklers, killed a man in July and sent 18 people to hospitals.

Even though the state in 1989 mandated fire sprinklers in new apartments and despite the overwhelming consensus among firefighters that sprinklers save lives and property, state law does not require them to be retrofitted in older structures, where millions of Californians live.

Why?

“There is a perception out there that these things are prohibitively expensive,” said Craig Oliver, president of California Building Officials, a statewide organization. “I admit they are not real cheap, but what value do you put on people’s lives?”

The head of a state apartment owners group bluntly agreed that landlords’ reluctance to bear the cost is the reason that most older apartment buildings haven’t been retrofitted with sprinklers.

“Show me the money,” said Dan Faller, president of the Apartment Owners Association of California, Inc., which represents more than 20,000 owners. “We always go back to who is going to pay for it. If they’re going to pass a law like that, where’s the money?”

He said tenants who want fire sprinklers don’t “have to rent that apartment if it doesn’t have the amenities they want.”

To fire officials, sprinklers are not amenities. Buildings without sprinklers “represent a significant hazard to the occupants and firefighters,” especially those with floors more than 75 feet above the ground, the International Fire Chiefs’ Association says on its website. It wants governments around the world to mandate retrofitting with automatic sprinkler systems.

“Fire sprinklers do save lives,” said Redwood City Fire Marshal Jim Palisi,¿ who was quick to point out Thursday that sprinklers likely would have slowed the spread of the Terrace Apartments fire.

Contractors specializing in sprinkler installation say retrofitting can cost as much as $5 per square foot. The average cost of sprinklers in new buildings runs $3 to $4 per square foot.

Several Terrace Apartments residents said they knew their building lacked fire sprinklers but chose to live there anyway.

“You don’t think it’s going to happen to you and you don’t worry about it,” said displaced tenant Nicole Redman, 27. “You don’t think it’s going to happen to your building. I think I’ll be looking for sprinklers in my next apartment. And I’ll be looking at escape routes.”

U.S. Census data shows California has about 3.9 million apartment buildings, which is 29 percent of the state’s housing stock.

In the Bay Area, including Santa Cruz and San Joaquin counties, apartment buildings make up 30 percent of the housing stock. San Francisco has the most buildings with 20 or more units — nearly 100,000 — and Alameda County has 95,000, data show. Most were built before sprinklers were required.

When California’s building and fire codes were changed to require sprinklers in all new apartment buildings in 1989 and new single-family homes in 2011, the state left mandatory retrofitting up to cities and counties.

The state’s fire agency maintains that sprinklers and smoke alarms “are the best form of fire protection there is,” said Cal Fire spokesman Dennis Mathisen. “But in terms of looking at retrofitting, we would leave that to local jurisdictions to decide what’s best for them.”

Oliver, the head of the state building officials organization, said he was unaware of any cities that require sprinkler retrofits in older buildings unless they are undergoing major renovations or expansions.

It could take a disaster to force change, he said.

“It’s kind of grim to say this, but we need another disaster. We didn’t get earthquake provisions until the (Loma Prieta) quake,” Oliver said. “Something’s got to happen.”